On 7/17/21 10:43 AM, Peter Maydell wrote:
On Mon, 12 Jul 2021 at 16:46, Richard Henderson <richard.hender...@linaro.org> wrote:Request that the one TB returns immediately, so that we release the exclusive lock as soon as possible. Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- accel/tcg/cpu-exec.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 2206c463f5..5bb099174f 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -330,8 +330,7 @@ void cpu_exec_step_atomic(CPUState *cpu) CPUArchState *env = (CPUArchState *)cpu->env_ptr; TranslationBlock *tb; target_ulong cs_base, pc; - uint32_t flags; - uint32_t cflags = (curr_cflags(cpu) & ~CF_PARALLEL) | 1; + uint32_t flags, cflags; int tb_exit; if (sigsetjmp(cpu->jmp_env, 0) == 0) { @@ -341,8 +340,14 @@ void cpu_exec_step_atomic(CPUState *cpu) cpu->running = true; cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); - tb = tb_lookup(cpu, pc, cs_base, flags, cflags); + cflags = curr_cflags(cpu); + /* Execute in a serial context. */ + cflags &= ~CF_PARALLEL; + /* After 1 insn, return and release the exclusive lock. */ + cflags |= CF_NO_GOTO_TB | CF_NO_GOTO_PTR | 1; + + tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { mmap_lock(); tb = tb_gen_code(cpu, pc, cs_base, flags, cflags);So previously we would have executed possibly a chain of TBs before releasing the lock, and now we definitely execute just one?
Correct.
(I guess the execute-a-chain case is unlikely given the TB only has one insn and we know it's an exclusive insn...)
I think it's actually likely. While the tb would definitely end after one insn, we had passed nothing down that would lead to returning to the main loop.
r~
Reviewed-by: Peter Maydell <peter.mayd...@linaro.org> thanks -- PMM
